Lightning-arrester



(No Model.) 2 Sheets-Sheet 2.

E. THOMSON.

LIGHTNING ARRESTER. No. 501,114. Patented July 11, 1898.

UNTTED STATES PATENT OFFICE.

ELIHU THOMSON, OF LYNN, MASSACHUSETTS, ASSIGNOR TO THE THOMSON- HOUSTON ELECTRIC COMPANY, OF CONNECTICUT.

LlGHTNlNG-ARRESTER.

SPECIFICATION forming part Of Letters Patent NO. 501,114, dated July 11, 1893.

Application filed June 20, 1890. Serial No. 356.116. (N0 model.)

To all whom it may concern.-

Be it known that I, ELIHU THOMSON, a citizen of the United States, and a resident of Lynn, in the county of Essex and State of Massachusetts, have invented certain new and useful Improvements in Lightning-Arresters, of which the following is a specification.

My present invention relates todevices for causing a lightning or other induced discharge of electricity to be carried olf to ground or otherwise diverted from a line or working circuit, so as not to injure the insulation thereof. Such induced discharges of high potential are generally of very short duration, lasting for only an exceedingly small fracnon of a second, and they confine themselves largely to the outer part of a conductor, so that a tubular conductor is as good for this purpose as a solid one, and better, if the amount of material is the same. In like manner, a sheet is better than a rod, or a fiat, straight sheet better than a coil or coiled sheet, on account of the lessened self-induction. Hence in the arrester hereinafter described it Will be observed that use is made for carrying oifthe quick,abnormal discharges of a tubular or other sheet-like conductor by which is meant one so shaped as to present a maximum amount of surface for the metal employed, and that a rod or coiled conductor is used for the normal current flowing in the system. The sheet-like discharge conductor, it should be observed, also extends substantially the entire distance to ground so as to form a path of low self induction throughout from the line to earth.

I will now refer to the drawings, and briefly describe the different figures thereof.

Figure 1, is a side View of my invention. Fig. 2 shows a modification. Fig. 3 is a .detailed sectional view of a portion of Fig. 1, and Figs. 4., 5 and 6 show still further modifications.

In Fig. l, W \V is a line wire or conductor, represented as extending from a dynamo D to a line circuit subject to lightning or other quick discharges. Around a portion of this conductor, between the dynamo D and the line whence induced discharges might come, there is situated a conducting tube T connected at A with the wire W. Between the inner conductor 7 and the tube T, is either an air space, or a space filled in part or entirely, with insulating material of any desired kind. This is indicated in Fig. 1, in black, and is shown in Fig. 3 in section, where R is a covering of hard rubber or other suitable material serving as a support for the tube sections T, and keeping them insulated. The tube may be cut or severed at one or more points of its length 25, so as to produceaspark gap or a series of spark gaps, which are bridged by asudden discharge delivered from the line at A to the tube T, and which discharge may pass to a ground plate G by any suitable electrical conductor 13, preferably a sheet of metal. The number of spark gaps provided may be varied in accordance with the normal potential on the line, a single spark gap being sufficient where such potential could not maintain an arc, and the number of gaps beingincreased to an extent sufficient to interrupt or prevent the establishing of permanent arc discharges to ground.

It is well to interpose between the portion of the wire IV W surrounded by T and the machine D, to be protected, a self inductive coil I, for increasing the self induction of the path to the machine D, and thus effectually forcing a high potential discharge to seek ground at G. Of course it will be understood, that whereas I have shown the spark gaps formed by severing the tube T into sections insulated from one another, the tube T might be left entire and the spark gaps be made in the conductor B leading therefrom. It is essential that the coil I, when used, should have its turns thoroughly insulated by an insulator not easily pierced by the discharge.

In Fig. 2, a slight modification is shown,in which T is a large tube or section, with only one spark gap made by serrating the adjaject edges of the tube at the interrupted point. The connection to ground B is as before preferably made of a wide sheet or plate.

Fig. a shows a similar structure to Fig. 1, except that the self inductive coil is in the interior of the enlarged tube T, being an elongated spiral surrounded by said tube, but separated by an air space therefrom.

In Fig. 5, the tube T is dispensed with, and is replaced by the diverging set of interrupted bars, arranged around or adjacent to the conductor WV, and connected together and with the conductor as shown. They may be considered as incomplete tubes or tube sections around the conductor, and the number of spark gaps in series may be varied as before, as may also the number of interrupted conductors themselves.

As shown in Fig. 6, still a different arrangement is employed. The line conductor is represented by W WV as in Fig. 1, and at A there is a branch which connects with a plate or sheet conductor T, separated from the ground by a spark gap, upon which a jet of air, J may be kept playing, as shown. The self inductive coil I, is inserted in the main XV between the point A and the apparatus to be protected, supposedly connected to the lower end of TV. Lightning discharges coming from the upper end of the line conductor will be impeded by the coil I on account of its self induction, but will be permitted a free path to ground by the enlarged plate conductor T, over the spark gap. This I branch may be made practically Without self induction and is therefore selective in its character for very quick discharges. It will be understood in any other than lightning arresters where quick discharges are caused to be selective as to patlnarrangements similar to those described, may be employed.

I claim as my invention-- In a lightning arrester, the combination of the line conductor with the tubular, sheetlike discharge conductor connected to ground and surrounding the line conductor, and the self induction coil between the apparatus to be protected and the pointof connection between the line conductor and tube, as described.

Signed at Lynn, Massachusetts, .Tune 16, 1890.

ELHIU THOMSON.

Witnesses:

JOHN W. GIBBONEY, ALBERT L. ROHRER. 

